Optical intrusion alarm system

ABSTRACT

An intrusion alarm system comprises a pair of light sources which produce overlapping light beams that effectively cover the entire area being protected. When either of the beams is interrupted by an intrusion, an alarm is caused to be actuated. In the embodiment of the invention here described, one of the light sources acts as a master unit directed toward a first array of detectors and the second light source directed at a second array of detectors acts as a transponder unit. When each of the detectors in the first array receives light from the master unit, the second source is turned on. The alarm is actuated whenever one of the second array of detectors fails to receive a light beam from the transponder unit.

United States Patent Schlisser et al.

OPTICAL INTRUSION ALARM SYSTEM Inventors: Gabor Schlisser, Tenafly;Julius R.

Insler, Bergenfield, both of NJ.

Assignee: Holobeam, Inc., Paramus, NJ.

Filed: Oct. 27, 1971 Appl. No.: 192,926

US. Cl. 340/258 B, 250/221, 340/276 Int. Cl. G08b 13/18 Field of Search340/258 B, 228 S;

[56] References Cited UNITED STATES PATENTS 3,235,738 2/1966 Kress et a1340/258 B Pr imary Examiner-David L. Trafton Attorney-Sandoe, Hopgood &Calimafde [111' as] June 12, 1973 [57] ABSTRACT An intrusion alarmsystem comprises a pair of light sources which produce overlapping lightbeams that ef fectively cover the entire area being protected. Wheneither of the beams is interrupted by an intrusion, an alarm is causedto be actuated. In the embodiment of the invention here described, oneof the light sources acts as a master unit directed toward a first arrayof dearray of detectors fails to receive a light beam from thetransponder unit.

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INVENTORS GABOR SCHLISSER BY JZ/L/US I? JMSLER m ATIURNEYS l OPTICALINTRUSION ALARM SYSTEM The present invention relates generally tointrusion warning systems, and more particularly to an optical intrusionalarm system in which an alarm is actuated upon the interruption of alight beam.

The use of optical techniques to provide an indication of an unwarrantedintrusion into an area is not a new one. One well-known technique is theprovision of a light beam normally incident on a photocell or similarphotodetector. When that beam is crossed by an intruder so that the pathof the beam to the photocell is interrupted, an electrical circuit isenergized to thereby actuate a suitable alarm. I

The known optical or light intrusion alarm systems are, however, able toeffect surveillance only over a relatively small area, limited primarilyby the area of the light beam employed. To increase the extent of thearea which can be accurately monitored for intrusion, the number ofbeams as well as the number of detectors employed may be increased. Theuse of additional beam sources, however, results in a system that isrelatively complex and costly and less reliable than one employing alesser number of sources or detectors. In addition, even with a largernumber of sources, I gaps through which the intruder may pass unnoticedare often unavoidably present unless an excessive'number of beam sourcesare employed, and great care is exercised in positioning those beamsources such that the resulting beams scan over the entire area to' beprotected.

As a result the known optical intrusion warning systems have heretoforebeen used only to protect relatively small areas, as no practicaloptical intrusion system has yet been developed for use in protectinglargescale installations such as industrial faciliteis, airports and thelike, even though such systems may take the place of conventionalstructural fences or the like.

It is thus an object of the invention to provide an improved intrusionwarning system employing optical techniques.

It is another object of the invention to provide an in trusion warningsystem capable of covering a greater area than has heretofore beenpossible.

It is a further object of the invention to provide a warning system ofthe type described employing only two sources of coherent or incoherentradiation, and which is capable of protecting a relatively large areaagainst unwarranted intrusions.

To these ends, the intrusion warning system of the invention comprises afirst beam source located at one boundary of the protected area anddirected at a first array of detectors arranged at the opposite boundaryof the protected area. Those detectors are coupled through a logiccircuit to a second beam source located at the opposite boundary anddirected toward a second array of detectors. The beams produced by thetwo beam sources are each triangular as viewed in a verticalcross-section, and preferably partially overlap one anothe so as tocover the entire area between the two boundaries. The patterns of thetwo beams result in an overall radiation pattern that constitutes aninvisible wall of light energy extending between the bound.- aries. Thesecond detector array is coupled to a second logic circuit which in turnis coupled to an alarm. The alarm is actuated only when one or more ofthe detectors in the second array fail to receive radiation thereon fromthe second beam source. If desired, the second array can be located inthe same area as the first beam source.

In operation, when all of the detectors in the first detector arrayreceive beam energy from the first beam source, the second beam sourceis actuated. However, if the radiation path from the first beam sourceto one or more of the detectors in the first array is interrupted, suchas by an intruder through the area, the second beam source is notactuated. As a direct and immediate result, no beam energy is received!by the second array of the detectors, and the alarm is caused to beoper' ated.

Alternatively, if the second beam source is not actuated, that is, if nointerruption occurs in the beam radiation to the first detector array,but if an intrusion through the area causes an interruption of beamradiation to the second detector array, the alarm is similarly actuated.If no intrusion occurs anywhere in the protected area, that is, if nointerruption occurs in either of the overlapping beams produced by thetwo beam sources, no alarm indication is produced.

As herein employed in the specification and claims,

' the term light is intended to include coherent and incoherentradiation in both the visible and nonvisible portions of the spectrumincluding the infrared range.

To the accomplishment of the above and to such further objects as mayhereinafter appear, the present invention relates to an opticalintrusion alarm substantially as defined in the appended claims, and asdescribed in the following specification taken together with theaccompanying drawings in which:

FIG. 1 is a schematic diagram of the intrusion warning system of theinvention illustrating the configurations of the light beams thatconstitute the optical wall;

FIG. 2 is a more detailed schematic diagram in block form of the systemof the invention shown in FIG. 1; and

FIG. 3 is a detailed schematic diagram of the signal processor of thesystem of FIG. 2..

The operating principles of the invention are schematically illustratedin FIG. 1 in which the system of the invention is illustrated for use inprotecting against the unwanted intrusion into an area or zone 10defined by spaced boundaries l2 and 14. The boundaries 12, 14 are spacedtransversely by a distance D; and the height of the boundaries is d, sothat the area of the protected zone 10 is Dxd.

In accordance with the invention, a first light source 16, which ispreferably a source of either coherent or incoherent infrared energy andwhich is here shown in the form of a laser, is positioned. at the lowerend of boundary l2, and a second beam source 18 also herein shown as alaser, is positioned at the upper end of boundary 14. The output lightenergy of source 16 is conical in form and is thus triangular as viewedin vertical cross-section in the plane of zone 10. That output beam isshaped into a triangular lower beam 20 having a desired area by opticalmeans described below. Beam 20 is directed at a plurality of detectors22, here shown as five in number, arranged and equidistantly verticallyspaced along boundary l4.v The output of source 18 is similarly formedinto a triangular upper beam 24 which is directed toward a second arrayof detectors 26 (also shown as five in number) equidistantly verticallyspaced along boundary 12. The base angles a of the two triangular beams22, 24 is selected to approximately correspond to the angle whosetangent is the ratio d/D.

As shown in FIG. 1, triangular beams 20 and 24 intersect at the centralregion of zone at region 28 such that beams and 24 cover substantiallythe entire area of zone 10, thereby forming what may be considered aninvisible wall of light extending between the zone-defining boundariesl2 and 14. Any unwarranted intrusion through that wall is detected in amanner to be described, and causes the actuation of an alarm to advisethose concerned with the integrity and security of the protected zone,that an intrusion has occurred therethrough.

The operation of the system of the invention may be better understoodwith reference to the schematic block diagram of the system illustratedin FIG. 2 wherein elements corresponding to those in FIG. 1 aredesignated by similar reference numerals. As shown in FIG. 2, the systemcomprises two separate but interrelated units, namely, a master unitwhich includes laser source 16 and detectors 26, and a transponder unit32 which includes laser beam transmitter 18 and detectors 22. Masterunit 32 further includes a suitable energizing source, here shown as anoscillator 34, which provides the energy necessary to actuate lasersource 16 to cause source 16 to produce an output beam in a knownmanner. That beam is shaped by beam forming optics 36 into beam 20having the triangular pattern hown in FIG. 1. Optics 36 may consistsimply of a lens positioned along the beam axis so as to achieve thedesired base angle a with the resulting complete coverage of the zone bythe partially overlapping means as described above.

The thus shaped beam produced by laser source 16, in the absence of anyintrusion through lower beam 20, is incident upon all of detectors '22.The outputs of detectors 22 re respectively coupled to the inputs of anAND gate 38, the output of which is in turn coupled to the actuating orcontrol portion of laser source 18. As a result, when all of detectors22 receive light energy from laser source 16, that is, when no intrusionoccurs in lower beam 20, all inputs to gate 30 re present and theresulting output of that gate causes laser source 18 to operate andproduce an output'beam.

That beam is shaped in beam forming optics which may be similar to beamforming optics 36, to produce upper beam 24 which, as described above,has a segment that overlies or intersects the upper segment of lowerbeam 20. Beam 24 is directed at detectors 26, and is received by all ofthose detectors except when beam 24 is interrupted.

The outputs of detectors 26 are applied respectively to the inputs of asecond AND gate 42, the output of which is applied to a signal processor44, which is described in greater detail below with respect to FIG. 3.

g The output of processor 44 is applied to the control terminal of an'alarm or warning indicator 46, which may conveniently be a siren, horn,whistel and/or flashing light.

Indicator 46 is caused to operate whenever processor 44 receives nosignal from gate 42. That can occur as a result of an intrusion throughbeam 20, which will interrupt the beam at one or more of detectors 22,with the result that gate 38 does not produce an operating signal forlaser source 18. When this occurs, no input is received at gate 42 fromany of detectors 26 since beam 24 is at that time terminated and none ofdetectors 26 receives radiation thereon.

When intrusion occurs in beam 24, the operation of transponder lasersource 18 is unaffected since beam 20 remains undisturbed and each ofdetectors 22 produces a signal to gate 38 which in turn operates lasersource 18. However, the interruption in beam 24 causes at least one ofdetectors 26 to at least temporarily fail to receive light incidentthereon, such that at least one input will be absent at gate 42. As aresult, gate 42 produces no output signal and processor 44 accordinglyproduces a signal to cause the actuation of alarm indicator 46.

Thus, as desired, an interruption in either of beams 20, 24 constitutingthe invisible light wall that completely covers the protected zone 10,causes alarm indicator 46 to be actuated, thereby immediately callingthat intrusion to the attention of the security personnel assigned tomonitor the protected area. v

Signal processor 44, which is shown in greater detail in FIG.3,'receives the output of AND gate 42 at an input terminal 48 coupled inturn to the junction point 50 of a voltage divider consisting ofresistors RI and R2, the latter being connected to ground. Point 50 iscoupled to one input of a NAND gate 52, the output of which is coupledtrough a capacitor C1 to the input of an NAND gate 54 and to groundthrough a resistor R3.

The output of gate 54 is returned to the other input of gate 52.

Gates 52 and 54 constitute a one-shot multivibrator 55 which upon thereceipt of a signal from AND gate 42, indicating that all the detectorsin array 26 are receiving radiation from transponder source 18, producesa as gate. To ensure that one-shot multivibrator 55 is triggered on onlyby an input signal rather than by noise, a reference voltage isestablished at point 50 by means of a Zener diode CR1 connected to a B+source 56 through a resistor R4. A capacitor C2 is coupled across diodeCR1 and ground.

The output gate produced by the one-shot multivibrator is coupled fromthe output of gate 52 through a resistor R5 and a diode CR2 to the baseof a switching transistor Q1. A resistor R6 is coupled between the. baseof transistor Q1 and ground, and the emitter of that transistor isdirectly connected to ground. The collector of transistor O1 is coupledto gate 2 of a dual gate field effect transistor (FET) Q2, as well asthrough a resistor R7 to the drain and gate 1 of FET Q2. The draincontact of that transistor is connected to the B+ source. A chargingcapacitor C3 is coupled across the emitter and collector contacts oftransistor Q1.

Capacitor C3 is also coupled to the base of a transistor Q3 whichtogether with transistor Q4 defines a differential amplifier 58 which,when actuated, produces an alarm signal whenever the voltage chargedacross capacitor C3 exceeds a reference voltage, the latter beingestablished by a Zener diode CR3 connected between the base oftransistor Q4 and ground.

A resistor R8 is connected between the emitters of transistors Q3 and Q4and ground, the collector transistor Q3 is connected to the B-lsourcethrough a resistor R9, the base of transistor Q4 is connected to the B+source through a resistor R10, and the collector of that transistor isdirectly connected to the B+ source.

The alarm gate signal produced by the differntial amplifier is coupledfrom the collector of transistor O3 to the base of an emitter followerconsisting of a transistor 64 and 66, point 60 being connected to oneinput of gate 64. The output of gate 64 is connected to one input ofgate 66, and the output of the latter is in turn connected to a secondinput of the 'former. The state of the latching flip-flop is changedupon the presence of the alarm gate signal at gate 64, and remains atthat state until reset by a reset signal applied to the other input ofgate 66 through a resistor R12. A capacitor C4 is connected betweenresistors R12 and ground.

The output of flip-flop 62 is coupled through a resistor R13 and a diodeCR5 to the base of an amplifier driver transistor Q6. A resistor R14 isconnected between the base of that transistor and ground and its emitteris directly connected to ground. The collector of transistor 06 iscoupled to the 13+ source through a resistor R15, and to the gateelectrode of a switching field effect transistor (FET) Q7. The source ofFET O7 is coupled to the B+ source through a resistor R16, and

, a resistor R17 is connected between the source of that transistor andground.

The alarm 46 is coupled across the drain and source of PET Q7 as is adiode CR6. Alarm 46 is thus actuated whenever conduction is produced inthe source-drain circuit of F ET Q7 as a result of an alarm signal beingapplied to the gate of that transistor in response to an intrusion inthe laser wall. That is, an intrusion in the wall causes, for reasonsdescribed above, AND gate 42 not to produce an output signal. As aresult, one-shot multivibrator 55 in signal processor 44 fails toproduce a 100 as gate such that the voltage across capacitor C3 ispermitted to change to a level exceeding the reference voltage ofdifferential amplifier 58. The resulting output of amplifier 58 in turnchanges the state of flipflop 62 to a condition rendering FET Q7conductive thereby actuating alarm 46 as desired. In the absence of anintrusion, the 100 [LS signal produced by one-shot multivibrator 55,when applied to switching transistor O1, is effective to dischargecapacitor C3 before the voltage thereon reaches the level at whichdifferential amplifier 58 is actuated.

The system of the invention thus has the capability of detecting theunwanted intrusion through a protected area, and of practicallyimmediately actuating an alarm to provide a warning of that intrusion tosecurity personnel, who are thus able to quickly locate and apprehendthe intruder. The system is highly reliable and accurate and yetrequires only a minimum number of relatively inexpensive components;gallium-arsenide laser diodes may be used to advantage for laser sources.16 and 18.

Moreover, the system of the invention provides sur- .veillance andprotection ofa large area, and thus significantly expands the practicalapplication of optical surveillance techniques. If desired, the systemof the invention may be employed in a multiple-segment perimeterprotection system of the type disclosed in our copending applicationSer. No. 113, 329, filed on Feb. 8,

1971, entitled Segment Locating Intrusion Alarm System with each segmentof the perimeter being defined by a single laser wall" as establishedherein.

As herein disclosed, the alarm indicator 46 is actuated in response tothe switching operation of an FET. If desired, the output of drivertransistor Q6 may be connected to a relay coil or the like, to actuatethe alarm whenever no signal is received by the signal processor as aresult of an intrusion in the laser wall. Moreover, as herein shown, alatching flip-flop is provided so that once actuated, the alarm ismaintained indefi-. nitely until reset. If desired, that flip-flop maybe omitted if only a temporary alarm indication is desired upon thedetection of an intrusion.

Thus, while the invention has been herein described with respect to asingle particular embodiment thereof, it will be apparent thatmodifications may be made therein all without departing from the spiritand scope of the invention.

What is claimed is:

1. An intrusion warning system for providing an indication of anintrusion into a protected area, said area being defined by first andsecond boundaries, said sys tem comprising a first beam source, a firstarray of detectors located at one of said boundaries and in opticalcommunication with said first beam source, a second beam source, meanscoupled to said first array of detectors and to said second beam sourcefor disabling the latter whenever radiation from said first beam sourceis interrupted from one of said first array of detectors, a second arrayof detectors located at an opposite one of said boundaries and inoptical communication with said second beam source, alarm means, andmeanscoupled between said second detector array and said alarm means foractuating the: latter whenever radiation from said second beam source toone of said second detector arrays is interrupted.

2. The system of claim 1, further comprising means respectivelyinterposed between said first and second beam sources and said first andsecond detector arrays for shaping the output of said first and secondsources into first and second beams that substantially completely coversaid area. 3

3. The system of claim 2, in which said beam shaping means includesmeans for causing adjacent portions of said first and second beams tooverlie one another at the central portion of said area.

4. The system of claim 3, in which said beam shaping means include meansfor developing the patterns of each of said first and second beams-intoan approximate triangular configuration.

S. The system of claim 4, in which said area has a transverse dimensionD and a vertical dimension d, the base angle a of said triangular beamsbeingapproximately equal to tan d/D.

1. An intrusion warning system for providing an indication of anintrusion into a protected area, said area being defined by first andsecond boundaries, said system comprising a first beam source, a firstarray of detectors located at one of said boundaries and in opticalcommunication with said first beam source, a second beam source, meanscoupled to said first array of detectors and to said second beam sourcefor disabling the latter whenEver radiation from said first beam sourceis interrupted from one of said first array of detectors, a second arrayof detectors located at an opposite one of said boundaries and inoptical communication with said second beam source, alarm means, andmeans coupled between said second detector array and said alarm meansfor actuating the latter whenever radiation from said second beam sourceto one of said second detector arrays is interrupted.
 2. The system ofclaim 1, further comprising means respectively interposed between saidfirst and second beam sources and said first and second detector arraysfor shaping the output of said first and second sources into first andsecond beams that substantially completely cover said area.
 3. Thesystem of claim 2, in which said beam shaping means includes means forcausing adjacent portions of said first and second beams to overlie oneanother at the central portion of said area.
 4. The system of claim 3,in which said beam shaping means include means for developing thepatterns of each of said first and second beams into an approximatetriangular configuration.
 5. The system of claim 4, in which said areahas a transverse dimension D and a vertical dimension d, the base angleAlpha of said triangular beams being approximately equal to tan 1 d/D.